The present invention relates to an apparatus and method for tensioning a fabric in a paper machine, such as a press felt, a drying wire, or an equivalent fabric, comprising a tensioning roll arranged inside a loop of the fabric, bearing supports for supporting the roll which are fixed to sledges at the driving side and at the operating side of the machine. The sledges are displaced by a motor, synchronously in relation to one another, to tighten the fabric that runs over the tensioning roll to a certain, desired tension.
In a paper machine, various wires and fabrics are used, such as forming wires, drying wires, and press felts, for all of which the general designation "fabric" will be used in the following description. The loops of these fabrics must be tensioned to a certain tension T, which is generally set in the range of from about 1 kN/m to about 5 kN/m. Moreover, inside the fabric loops, an alignment roll is often used so that by regulating the axial alignment of the alignment roll, the transverse position of the fabric is controlled.
In the prior art, a number of different devices for tensioning the fabrics in a paper machine are known. The device that is most commonly used is probably a tensioning device in which the tensioning roll is mounted at the operating side and at the driving side of the machine on carriages. The carriages are displaced synchronously with one another on rollers inside a box beam attached to the frame part of the paper machine.
In addition, some of the prior art devices are not very rigid, but rather have a large amount of play. This causes drawbacks, such as a tendency of vibration, which are detrimental to the operation of the tensioning devices.